The favorable algebraic properties and error-correcting performance of BCH codes have motivated extensive research and diverse applications, whereas the study of extended BCH codes remains relatively less explored. In this paper, we focus on the extended BCH codeC(q,q+1,δ,h)over the finite field Fq. Specifically, we investigate the parameters of three families of extended BCH codes and the weight distributions of their duals by solving certain quadratic and quartic equations:C(q,q+1,3,1)is shown to be NMDS when gcd(q+1,3) = 1;C(q,q+1,δ,q)with 3 ≤ δ ≤ ⌈(q+ 5)/2⌉ is proved to be AMDS; andC(q,q+1,3,q/2)is MDS for evenq.